LONDON -- Antonio Conte and Arsene Wenger both offered a measured endorsement of the video assistant referee (VAR) after the technology was trialled for the second time in English football as Chelsea drew 0-0 with Arsenal in the first leg of their Carabao Cup semifinal tie at Stamford Bridge.

Match referee Martin Atkinson consulted VAR several times in the first half and once after the interval to re-examine penalty appeals for both teams, as well as a push by Calum Chambers on Cesar Azpilicueta as the pair jostled in the Chelsea box ahead of an Arsenal corner kick.

Each time the system successfully provided clarification on key situations, though the lengthy delays and lack of explanation of what was going on left many at Stamford Bridge in the dark as Atkinson held his hand to his ear to communicate with Neil Swarbrick, who was watching the video in the studio.

Speaking after the match, Conte said he was "positive" about the potential of VAR to improve football, but added that the process can still be improved -- there were more than seven minutes of stoppages in the match for video review and substitutions, but just six minutes of extra time played at the end of each half.

"You have to improve and understand that when you start to use VAR you then need to add more extra time," Conte said. "The doctor went onto the pitch twice and the referee stopped to listen to VAR and you have to give more minutes in extra time. In Italy the extra time is sometimes seven, eight or nine minutes."

The longest delay came in the second half, when Atkinson consulted the technology following a potential penalty collision between Danny Welbeck and Cesc Fabregas in the Arsenal box. In the end no spot kick was awarded, but Wenger admitted that the delay made him anxious.

"It was interesting," he said. "It was a cause of anxiety as it took a bit of time to make the second decision with Welbeck and Fabregas, but overall it worked well. But between the penalty action or penalty not action, with the time taken it would have been strange to come back to the penalty."

Welbeck, however, insisted he had no concerns that VAR would rule in his favour. "I didn't know the VAR referral was actually for that incident," he told Sky Sports after the match. "I knew I got the ball. We saw he had somebody in his ear but I got the ball clearly so I didn't mind."

Referees chief Mike Riley believes can add value to the game.

"It has gone very well in the first few games," Riley told BBC Radio 5 Live. "We've had the opportunity to use it, it has been used very effectively and we've come out with the right outcomes.

"The whole idea of the protocol is to have minimum interference on the game but get the right decisions to have the maximum impact."

Riley acknowledged that more needs to be done to inform spectators at matches when VAR is being deployed by referees.

"It is really important for spectators in the stadium to understand when it is being used and when not.

"Currently, if you look at the referee, you will see him put his finger in his ear but I accept that in the stadium that can be quite difficult to see so the question now is how can we improve that experience for spectators.

"We are reviewing the games from this week and coming up with some ideas for the games next week to try to make that more effective."

Riley also said more officials will come on board as the experiment continues.

"It is important to give people the opportunity to experience two or three games so they understand the process. Mike Jones has been appointed to VAR the games next week and, as we continue with the experiment, other people will take that role as well."

Referees chief Mike Riley believes can add value to the game.

"It has gone very well in the first few games," Riley told BBC Radio 5 Live. "We've had the opportunity to use it, it has been used very effectively and we've come out with the right outcomes.

"The whole idea of the protocol is to have minimum interference on the game but get the right decisions to have the maximum impact."

Riley acknowledged that more needs to be done to inform spectators at matches when VAR is being deployed by referees.

"It is really important for spectators in the stadium to understand when it is being used and when not.

"Currently, if you look at the referee, you will see him put his finger in his ear but I accept that in the stadium that can be quite difficult to see so the question now is how can we improve that experience for spectators.

"We are reviewing the games from this week and coming up with some ideas for the games next week to try to make that more effective."

Riley also said more officials will come on board as the experiment continues.

"It is important to give people the opportunity to experience two or three games so they understand the process. Mike Jones has been appointed to VAR the games next week and, as we continue with the experiment, other people will take that role as well."